1. Field of the Invention
The present invention relates to a magnetic material obtained by plating, a magnetic recording medium using the magnetic material, a magnetic recording/reproducing apparatus, an information reproducing apparatus, and a method for manufacturing the magnetic material.
2. Description of the Related Art
In accordance with a recent great increase in the amount of information processing, a large amount of capacity has been requested in an information recording technique using magnetic disk apparatuses, and the like. Particularly, in the field of hard disks, the amount of recorded information per unit area is increasing with a rate exceeding 60% per year. An increase in the amount of information recording is constantly being desired, and size reduction and high-density recording have been desired for portable recording apparatuses, and the like.
Conventional magnetic recording media for hard disks adopt a longitudinal magnetic recording method in which recording is performed so that a magnetic material is magnetized in a direction parallel to the surface of a disk. In such a longitudinal magnetic recording method, in accordance with high-density recording, in order to suppress a demagnetization field within a magnetic domain and cause a magnetic field to extract from above a recording medium so that a state of magnetization can be detected, it is necessary to reduce the thickness of a magnetic recording layer. As a result, the volume of a magnetic fine particle is extremely reduced, thereby a superparamagnetic effect becomes remarkable. That is, energy stabilizing the direction of magnetization is reduced by thermal energy, and recorded magnetization changes as the progress of time, thereby sometimes causing erasure of recording. Accordingly, studies of a perpendicular magnetic recording method in which a recording layer can have a large thickness have been intensively studied as a replacement for longitudinal magnetic recording.
A Co—Cr alloy is usually used for a recording layer 24 of a perpendicular magnetic recording medium shown in FIGS. 2A and 2B. As shown in FIG. 2B, when the recording layer 24 is formed according to sputtering, core portions 26 in which Co is rich, and shell portions 27 surrounding the corresponding core portions 26 in which Cr is relatively rich are grown by being separated from each other. The core portion 27 has a shape close to a cylinder and hard magnetism with a hexagonal close-packed structure (hereinafter abbreviated as a “hcp structure”), and serves as a recording portion. The shell portion 27 has a Cr-rich composition, and soft magnetism or a non-magnetic property, and has a role of weakening interaction between adjacent core portions. In the core portion 26, the c axis is perpendicular to the surface of a substrate 21, and magnetization is perpendicular to the surface of the substrate 21 according to crystallomagnetic anisotropy. At least one of Ta, Pt, Rh, Pd, Ti, Nb, Hf, and the like is added to the recording layer 24 in addition to Co—Cr.
However, in accordance with coming higher recording density, it is expected that provision of finer core portions 26 is difficult in a Co—Cr-type material. Furthermore, since the superparamagnetic effect is more pronounced in accordance with provision of finer core portions, a recently noticed L10-ordered alloy made of CoPt, FePt or FePd is considered to be a very promising material. Particularly, a medium obtained by providing fine L10-ordered alloy particles and dispersing the particles in a non-magnetic parent material to provide a film (a granular film) that can resist against a superparamagetic effect caused by fine Co—Cr magnetic particles has been proposed (Japanese Patent Application Laid-Open (Kokai) No. 2001-273622). However, it is also important to control the volume distribution of fine magnetic particles.
Because a glass substrate or the like is currently used, reduction of a temperature to transform into L10-ordered alloy made of CoPt, FePt or FePd is considered to be necessary and has been studied. Particularly, reduction of the temperature caused by addition of a third element to a FePt alloy is considered to be promising in film formation according to sputtering. However, studies about CoPt or FePt deposited from a plating solution are performed very little, and studies about additive elements are not yet performed.